On Wed, 5 Mar 2014, Dan Williams wrote:
> Please have a look at the following. I'm sure Greg will be happy that
> we are killing these bugs before they become fodder for -stable. Thanks
Wow, do you really think all these changes will ever go into -stable?
I'm doubtful; they're rather large.
> for the review! The other change I made was to convert
> find_default_peer to find_and_link_peer per your other comments about
> centralizing peering on patch 6.
Good idea, since it now finds all peers and not just the default ones.
> 8<---------
> Subject: usb: assign default peer ports for root hubs
>
> From: Dan Williams <dan.j.williams@xxxxxxxxx>
>
> Assume that the peer of a superspeed port is the port with the same id
> on the shared_hcd root hub. This identification scheme is required of
> external hubs by the USB3 spec [1]. However, for root hubs, tier mismatch
> may be in effect [2]. Tier mismatch can only be enumerated via platform
> firmware. For now, simply perform the nominal association.
>
> A new lock 'usb_port_peer_mutex' is introduced to synchronize port
> device add/remove with peer lookups. It protects peering against
> changes to hcd->shared_hcd, hcd->self.root_hub, hdev->maxchild, and
> port_dev->child pointers.
>
> [1]: usb 3.1 section 10.3.3
> [2]: xhci 1.1 appendix D
>
> Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> [alan: usb_port_peer_mutex locking scheme]
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
> index 531a591a7b1e..0d36610af156 100644
> --- a/drivers/usb/core/port.c
> +++ b/drivers/usb/core/port.c
> @@ -151,9 +151,66 @@ static struct device_driver usb_port_driver = {
> .owner = THIS_MODULE,
> };
>
> +static void link_peers(struct usb_port *left, struct usb_port *right)
> +{
> + if (left->peer == right && right->peer == left)
> + return;
> +
> + if (left->peer || right->peer) {
> + struct usb_port *lpeer = left->peer;
> + struct usb_port *rpeer = right->peer;
> +
> + WARN(1, "failed to peer %s and %s (%s -> %p) (%s -> %p)\n",
> + dev_name(&left->dev), dev_name(&right->dev),
> + dev_name(&left->dev), lpeer,
> + dev_name(&right->dev), rpeer);
> + return;
> + }
> +
> + left->peer = right;
> + right->peer = left;
> +}
> +
> +static void unlink_peers(struct usb_port *left, struct usb_port *right)
> +{
> + WARN(right->peer != left || left->peer != right,
> + "%s and %s are not peers?\n",
> + dev_name(&left->dev), dev_name(&right->dev));
At some point, maybe we'll have enough confidence in the locking to
remove all these checks. :-)
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Alan Stern
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